This invention relates generally to sampling data that includes wide bi-phase code symbols and, more particularly, to a disk drive that asynchronously samples information, such as burst correction values (BCVs) and servo information, stored as wide bi-phase code symbols.
A data storage disk in a disk drive contains data tracks and radial spokes (also called xe2x80x9cwedgesxe2x80x9d). The data tracks contain substantive information and the spokes contain servo information and burst data. The spokes are used in positioning a transducer head on the disk.
More specifically, by reading the servo information and burst data recorded within the spokes, a disk drive head positioner servo system is able to estimate the position of the drive""s data transducer head. The recorded servo information typically includes track (i.e., cylinder and head) addresses. Each circumferential data track on a disk surface has a unique track address, which is recorded in the spokes. The servo burst data are recorded on the disk for use in positioning the transducer head properly on a track.
Thus, when a disk drive is seeking to a radial track location, the track addresses are used as coarse positioning information to position the transducer head on a specific track. The servo bursts are used as fine positioning information to position the head at a desired radial location within the track specified by the servo information.
In general, in one aspect, the invention is directed to sampling data with wide bi-phase code symbols. This aspect of the invention includes sampling a wide bi-phase code symbol in the data a number (N) of times to produce samples of data, selecting a subset of the samples, determining which sample in the subset of samples has a largest magnitude, and selecting a subset of samples in a subsequent wide bi-phase code symbol based on a sample in a previous subset that has the largest magnitude.
By sampling a first wide bi-phase code symbol and selecting samples in a subsequent wide bi-phase code symbol based on the previous sample, the invention facilitates asynchronous sampling, reducing the need for feedback loops and the like to provide timing.
This aspect may include one or more of the following features. The largest magnitude may correspond to a peak in the wide bi-phase code symbol. The subset of samples may include three samples. Determining which sample in the subset of samples has the largest magnitude may include identifying if a middle sample of the three samples has the largest magnitude. If the middle sample does not have the largest magnitude, the process may include moving in the data an equivalent of Nxc2x11 samples and sampling the subsequent wide bi-phase code symbol starting at a location corresponding to the equivalent of the Nxc2x11 samples.
The data may include servo information on a storage disk. The servo information may identify a track on the storage disk. The data may include burst correction values stored on a storage disk. A burst correction value is an offset used in positioning a reading device on a track of the storage disk. Wide bi-phase code is a code in which a zero is represented by data values comprising xe2x80x9c++xe2x88x92xe2x88x92xe2x80x9d and a one is represented by data values comprising xe2x80x9cxe2x88x92xe2x88x92++xe2x80x9d. The value of N may be greater than four, e.g., eight.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the following description, drawings and claims.